1. Technical Field
This specification generally describes an apparatus for image forming, and more particularly describes an apparatus capable of stably developing images.
2. Discussion of the Background
In a general image forming apparatus using two-component developer, the image forming apparatus may have a rotary non-magnetic sleeve including a plurality of magnets. The two-component developer refers to developer including toner particles and carrier beads and is hereafter simply referred to as developer.
The sleeve, serving as a developer carrying member, may have its surface grooved or roughened (e.g. sandblasted) to prevent a slippage of the developer, thereby increasing a developer carrying capacity.
The grooved sleeves are found to be less susceptible to wearing over time than the sandblasted sleeves. However, the grooved sleeves may produce an image with periodically varying densities corresponding to a pitch of the grooves, which is hereafter referred to as a banding effect.
Deeper grooves may achieve a higher developer carrying capacity but may cause a banding effect because of different development fields between groove areas and non-groove areas. Shallower grooves may cause a banding effect because of reduced developer carrying capacity.
There is a background image forming apparatus having a sleeve having grooves whose depth is defined to be from 0.05 mm to 0.15 mm.
When finer toner particles are used, the banding effect may become more noticeable because of an improved image reproduction capability.
There is another background image forming apparatus using two-component developer including toner particles whose diameter is from 4 μm to 8.5 μm. The image forming apparatus has a sleeve having a plurality of longitudinally extending grooves. The grooves are disposed with a pitch smaller than a movement of a PC drum within a development zone. In this manner, the development zone of the PC drum may be always in contact with at least one groove on the sleeve, thus reducing a banding effect.